PROJECT SUMMARY/ABSTRACT A total of 11.8 million children live in rural areas of the United States, and one-quarter of these children have chronic health conditions. This population is more likely to have disabilities, less likely to receive preventative care, and more likely to report unmet healthcare needs than children who live in urban areas. As such, they represent an underserved group at high risk for disparities in health outcomes. Children with complex or disabling health conditions may be at particular risk of adverse outcomes when they live in rural areas due to their chronic and multifaceted healthcare needs. However, at a population level we know extremely little about how urban-rural disparities in health care access impact this vulnerable population. The overall objective of this proposal is to comprehensively evaluate urban-rural disparities in health care utilization and quality for children with complex or disabling health conditions using five years of all-payer claims data from three states: Colorado, Massachusetts and New Hampshire. These states represent diverse populations with respect to geography, rurality, and race/ethnicity, making them ideally suited to the proposed analyses. We will conduct a retrospective cohort study of approximately 140,000 children to: (i) identify urban-rural disparities in ambulatory, emergency and inpatient healthcare utilization, (ii) characterize urban-rural disparities in healthcare quality, (iii) identify community and health-system factors associated with urban-rural disparities in healthcare quality, and (iv) construct patient-sharing networks among physicians who care for these children to determine how patient-sharing networks differ between rural- and urban-residing children, and whether these differences are associated with disparities in quality of care. Construction of physician patient-sharing networks ? that is, structural representations of relationships between physicians developed on the basis of shared patients -? provides a systematic approach to identify relationships between physicians that exist outside of formal organizational structures, which may be particularly relevant to children living in rural areas. In adult populations, network characteristics have been associated with resource utilization, practice patterns, and healthcare outcomes. However, this study will be the first to explore how physician networks differ between urban- and rural-residing children, characterizing a modifiable health system factor that may be leveraged in future work to reduce urban-rural disparities in their quality of care. This project will be conducted by a multidisciplinary team with clinical expertise providing care for children with medical complexity, as well as research expertise using all-payer claims data to evaluate healthcare quality and construct social networks. This research will generate essential data to inform the subsequent implementation and evaluation of interventions to reduce health disparities for rural-residing children with complex or disabling health conditions.